Influence of maternal BMI on genetic sonography in the FaSTER trial

Abstract

Objective We sought to evaluate the influence of maternal body mass index (BMI) on sonographic detection employing data from the FaSTER trial. Method Unselected singleton pregnancies underwent detailed genetic sonogram to evaluate for structural fetal anomalies and soft markers for aneuploidy. BMI (kg/m²) were calculated from reported initial visit values. Sensitivity, specificity, false positive and false negative rates (FPR and FNR), likelihood ratio, detection rates, and a missed diagnosis rate (MDR: FNR + marker recorded as ‘missing’/N) were calculated. Results Eight thousand five hundred and fifty-five patients with complete BMI information had detailed genetic sonography. A lower sensitivity with an elevated FNR and MDR was observed in obese women for multiple aneuploid markers (e.g. ≥2 markers 32% sensitivity with 68% FNR among BMI 30). Similarly, the detection rate for cardiac anomalies among women at BMI p = 0.001). Conclusion The performance of second trimester genetic sonography is influenced by obesity, with a significantly higher MDR for multiple minor markers and lower likelihood for detecting common anomalies. Copyright © 2009 John Wiley & Sons, Ltd.